High internal phase emulsion foam having low levels of unpolymerized monomers

ABSTRACT

A High Internal Phase Emulsion (HIPE) foam having low levels of unpolymerized monomer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/290,947 filed on 30 Dec. 2009, the substance of which is incorporatedherein by reference.

FIELD OF THE INVENTION

This application relates to a High Internal Phase Emulsion (HIPE) foamhaving low levels of unpolymerized monomers

BACKGROUND OF THE INVENTION

An emulsion is a dispersion of one liquid in another liquid andgenerally is in the form of a water-in-oil mixture having an aqueous orwater phase dispersed within a substantially immiscible continuous oilphase. Water-in-oil (or oil in water) emulsions having a high ratio ofdispersed aqueous phase to continuous oil phase are known in the art asHigh Internal Phase Emulsions, also referred to as “HIPE” or HIPEs. Atrelatively high dispersed aqueous phase to continuous oil phase ratiosthe continuous oil phase becomes essentially a thin film separating andcoating the droplet-like structures of the internal, dispersed aqueousphase. In one embodiment the continuous oil phase of a water-in-oil HIPEcomprises one or more polymerizable monomers. These monomers can bepolymerized, forming a cellular structure, for example a foam, having acell size distribution defined by the size distribution of thedispersed, aqueous phase droplets.

Polymerization of the monomers starts upon the activation of aninitiator and continues during the curing process. The curing process isoften at the end or near the end of the foam forming process; afterwhich the HIPE foam is prepared for its future uses. However, after theaddition of initiator and the curing process not all of the monomers arepolymerized. These residual unpolymerized monomers can cause problemsboth in the HIPE foam and the process used to prepare the HIPE foams. Ifunreacted monomers are present in the HIPE foam they may pose a safetyconcern at certain levels, adversely affect the desired HIPE foamproperties or interfere with the further HIPE foam processing steps,such as cutting or the application of other components to the HIPE foam.In addition, the monomers also have a tendency to adhere to surfaceswhich can cause processing problems both in batch processes where themonomers may adhere to the mold cavity requiring cleaning of the moldsor in the case of a continuous process requiring the cleaning of thesurface upon which a HIPE is deposited onto.

Accordingly, there is a need for HIPE foams having low levels ofunpolymerized monomers and a method that reduces the amount ofunpolymerized monomer in HIPE foams.

SUMMARY OF THE INVENTION

A High Internal Phase Emulsion foam formed by polymerizing a HighInternal Phase Emulsion is provided that comprises an oil phase havingmonomer, cross-linking agent, emulsifier; photoinitiator; and an aqueousphase; wherein the High Internal Phase Emulsion foam comprises less than400 ppm unpolymerized monomer.

A High Internal Phase Emulsion foam formed by polymerizing a HighInternal Phase Emulsion is provided that comprises a first layer havingan oil phase which includes monomer, cross-linking agent, emulsifier;photoinitiator; and an aqueous phase. The High Internal Phase Emulsionalso includes a second layer having an oil phase which includes monomer,cross-linking agent, emulsifier; photoinitiator; and an aqueous phase;wherein the High Internal Phase Emulsion foam comprises less than 400ppm unpolymerized monomer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow diagram of the present invention.

FIG. 2 is a process flow diagram of the present invention.

FIG. 3 is a graph showing monomer reduction.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a High Internal Phase Emulsion (HIPE)foam having low levels of unpolymerized monomer. HIPEs of the presentinvention comprising a continuous oil phase containing monomers and anaqueous phase are produced using a continuous process, for example byhaving a HIPE deposited on a belt, such as an endless belt. While on thebelt the HIPE are moved to a heating zone, where the monomers arepolymerized to form a HIPE foam. Following the heating zone the HIPEfoam is moved to a UV light zone, wherein the unpolymerized monomers areexposed to UV light which polymerizes them.

A High Internal Phase Emulsion (HIPE) comprises two phases. One phase isa continuous oil phase comprising monomers that are polymerized to forma HIPE foam and an emulsifier to help stabilize the HIPE. The oil phasemay also include one or more photoinitiators. The monomer component, maybe present in an amount of from about 80% to about 99%, and in certainembodiments from about 85% to about 95% by weight of the oil phase. Theemulsifier component, which is soluble in the oil phase and suitable forforming a stable water-in-oil emulsion may be present in the oil phasein an amount of from about 1% to about 20% by weight of the oil phase.The emulsion may be formed at an emulsification temperature of fromabout 10° C. to about 130° C. and in certain embodiments from about 50°C. to about 100° C.

In general, the monomers will include from about 20% to about 97% byweight of the oil phase at least one substantially water-insolublemonofunctional alkyl acrylate or alkyl methacrylate. For example,monomers of this type may include C₄-C₁₈ alkyl acrylates and C₂-C₁₈methacrylates, such as ethylhexyl acrylate, butyl acrylate, hexylacrylate, octyl acrylate, nonyl acrylate, decyl acrylate, isodecylacrylate, tetradecyl acrylate, benzyl acrylate, nonyl phenyl acrylate,hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, nonylmethacrylate, decyl methacrylate, isodecyl methacrylate, dodecylmethacrylate, tetradecyl methacrylate, and octadecyl methacrylate.

The oil phase may also comprise from about 2% to about 40%, and incertain embodiments from about 10% to about 30%, by weight of the oilphase, a substantially water-insoluble, polyfunctional crosslinkingalkyl acrylate or methacrylate. This crosslinking comonomer, orcrosslinker, is added to confer strength and resilience to the resultingHIPE foam. Examples of crosslinking monomers of this type comprisemonomers containing two or more activated acrylate, methacrylate groups,or combinations thereof. Nonlimiting examples of this group include1,6-hexanedioldiacrylate, 1,4-butanedioldimethacrylate,trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,12-dodecyldimethacrylate, 1,14-tetradecanedioldimethacrylate, ethyleneglycol dimethacrylate, neopentyl glycol diacrylate(2,2-dimethylpropanediol diacrylate), hexanediol acrylate methacrylate,glucose pentaacrylate, sorbitan pentaacrylate, and the like. Otherexamples of crosslinkers contain a mixture of acrylate and methacrylatemoieties, such as ethylene glycol acrylate-methacrylate and neopentylglycol acrylate-methacrylate. The ratio of methacrylate:acrylate groupin the mixed crosslinker may be varied from 50:50 to any other ratio asneeded.

Any third substantially water-insoluble comonomer may be added to theoil phase in weight percentages of from about 0% to about 15% by weightof the oil phase, in certain embodiments from about 2% to about 8%, tomodify properties of the HIPE foams. In certain cases, “toughening”monomers may be desired which impart toughness to the resulting HIPEfoam. These include monomers such as styrene, vinyl chloride, vinylidenechloride, isoprene, and chloroprene. Without being bound by theory, itis believed that such monomers aid in stabilizing the HIPE duringpolymerization (also known as “curing”) to provide a more homogeneousand better formed HIPE foam which results in better toughness, tensilestrength, abrasion resistance, and the like. Monomers may also be addedto confer flame retardancy as disclosed in U.S. Pat. No. 6,160,028(Dyer) issued Dec. 12, 2000. Monomers may be added to confer color, forexample vinyl ferrocene, fluorescent properties, radiation resistance,opacity to radiation, for example lead tetraacrylate, to dispersecharge, to reflect incident infrared light, to absorb radio waves, toform a wettable surface on the HIPE foam struts, or for any otherdesired property in a HIPE foam. In some cases, these additionalmonomers may slow the overall process of conversion of HIPE to HIPEfoam, the tradeoff being necessary if the desired property is to beconferred. Thus, such monomers can be used to slow down thepolymerization rate of a HIPE. Examples of monomers of this typecomprise styrene and vinyl chloride.

The oil phase may further contain an emulsifier used for stabilizing theHIPE. Emulsifiers used in a HIPE can include: (a) sorbitan monoesters ofbranched C₁₆-C₂₄ fatty acids; linear unsaturated C₁₆-C₂₂ fatty acids;and linear saturated C₁₂-C₁₄ fatty acids, such as sorbitan monooleate,sorbitan monomyristate, and sorbitan monoesters, sorbitan monolauratediglycerol monooleate (DGMO), polyglycerol monoisostearate (PGMIS), andpolyglycerol monomyristate (PGMM); (b) polyglycerol monoestersof—branched C₁₆-C₂₄ fatty acids, linear unsaturated C₁₆-C₂₂ fatty acids,or linear saturated C₁₂-C₁₄ fatty acids, such as diglycerol monooleate(for example diglycerol monoesters of C18:1 fatty acids), diglycerolmonomyristate, diglycerol monoisostearate, and diglycerol monoesters;(c) diglycerol monoaliphatic ethers of—branched C₁₆-C₂₄ alcohols, linearunsaturated C₁₆-C₂₂ alcohols, and linear saturated C₁₂-C₁₄ alcohols, andmixtures of these emulsifiers. See U.S. Pat. No. 5,287,207 (Dyer etal.), issued Feb. 7, 1995 and U.S. Pat. No. 5,500,451 (Goldman et al.)issued Mar. 19, 1996. Another emulsifier that may be used ispolyglycerol succinate (PGS), which is formed from an alkyl succinate,glycerol, and triglycerol.

Such emulsifiers, and combinations thereof, may be added to the oilphase so that they comprise between about 1% and about 20%, in certainembodiments from about 2% to about 15%, and in certain other embodimentsfrom about 3% to about 12% by weight of the oil phase In certainembodiments, coemulsifiers may also be used to provide additionalcontrol of cell size, cell size distribution, and emulsion stability,particularly at higher temperatures, for example greater than about 65°C. Examples of coemulsifiers include phosphatidyl cholines andphosphatidyl choline-containing compositions, aliphatic betaines, longchain C₁₂-C₂₂ dialiphatic quaternary ammonium salts, short chain C₁-C₄dialiphatic quaternary ammonium salts, long chain C₁₂-C₂₂dialkoyl(alkenoyl)-2-hydroxyethyl, short chain C₁-C₄ dialiphaticquaternary ammonium salts, long chain C₁₂-C₂₂ dialiphatic imidazoliniumquaternary ammonium salts, short chain C₁-C₄ dialiphatic imidazoliniumquaternary ammonium salts, long chain C₁₂-C₂₂ monoaliphatic benzylquaternary ammonium salts, long chain C₁₂-C₂₂dialkoyl(alkenoyl)-2-aminoethyl, short chain C₁-C₄ monoaliphatic benzylquaternary ammonium salts, short chain C₁-C₄ monohydroxyaliphaticquaternary ammonium salts. In certain embodiments, ditallow dimethylammonium methyl sulfate (DTDMAMS) may be used as a coemulsifier.

Photoinitiators may comprise between about 0.05% and about 10%, and incertain embodiments between about 0.2% and about 10% by weight of theoil phase. Lower amounts of photoinitiator allow light to betterpenetrate the HIPE foam, which can provide for polymerization deeperinto the HIPE foam. However, if polymerization is done in anoxygen-containing environment, there should be enough photoinitiator toinitiate the polymerization and overcome oxygen inhibition.Photoinitiators can respond rapidly and efficiently to a light sourcewith the production of radicals, cations, and other species that arecapable of initiating a polymerization reaction. The photoinitiatorsused in the present invention may absorb UV light at wavelengths ofabout 200 nanometers (nm) to about 800 nm, in certain embodiments about250 nm to about 450 nm. If the photoinitiator is in the oil phase,suitable types of oil-soluble photoinitiators include benzyl ketals,α-hydroxyalkyl phenones, α-amino alkyl phenones, and acylphospineoxides. Examples of photoinitiators include2,4,6-[trimethylbenzoyldiphosphine]oxide in combination with2-hydroxy-2-methyl-1-phenylpropan-1-one (50:50 blend of the two is soldby Ciba Speciality Chemicals, Ludwigshafen, Germany as DAROCUR® 4265);benzyl dimethyl ketal (sold by Ciba Geigy as IRGACURE 651);α-,α-dimethoxy-α-hydroxy acetophenone (sold by Ciba Speciality Chemicalsas DAROCUR® 1173); 2-methyl-1-[4-(methyl thio)phenyl]-2-morpholino-propan-1-one (sold by Ciba Speciality Chemicals asIRGACURE® 907); 1-hydroxycyclohexyl-phenyl ketone (sold by CibaSpeciality Chemicals as IRGACURE® 184);bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (sold by CibaSpeciality Chemicals as IRGACURE 819); diethoxyacetophenone, and4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-methylpropyl)ketone (sold by CibaSpeciality Chemicals as IRGACURE® 2959); and Oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone] (sold byLamberti spa, Gallarate, Italy as ESACURE® KIP EM.

The dispersed aqueous phase of a HIPE comprises water, and may alsocomprise one or more components, such as initiator, photoinitiator, orelectrolyte, wherein in certain embodiments, the one or more componentsare at least partially water soluble.

One component of the aqueous phase may be a water-soluble electrolyte.The water phase may contain from about 0.2% to about 40%, in certainembodiments from about 2% to about 20%, by weight of the aqueous phaseof a water-soluble electrolyte. The electrolyte minimizes the tendencyof monomers, comonomers, and crosslinkers that are primarily oil solubleto also dissolve in the aqueous phase. Examples of electrolytes includechlorides or sulfates of alkaline earth metals such as calcium ormagnesium and chlorides or sulfates of alkali earth metals such assodium. Such electrolyte can include a buffering agent for the controlof pH during the polymerization, including such inorganic counterions asphosphate, borate, and carbonate, and mixtures thereof. Water solublemonomers may also be used in the aqueous phase, examples being acrylicacid and vinyl acetate.

Another component that may be present in the aqueous phase is awater-soluble free-radical initiator. The initiator can be present at upto about 20 mole percent based on the total moles of polymerizablemonomers present in the oil phase. In certain embodiments, the initiatoris present in an amount of from about 0.001 to about 10 mole percentbased on the total moles of polymerizable monomers in the oil phase.Suitable initiators include hydrogen peroxide, lauryl peroxide, t-butylhydrogen peroxide, other suitable peroxides, ammonium persulfate, sodiumpersulfate, potassium persulfate,2,2′-azobis(N,N′-dimethyleneisobutyramidine)dihydrochloride, and othersuitable azo initiators, redox couples such as persulfate-bisulfate,persulfate-ascorbic acid and others. In certain embodiments, to reducethe potential for premature polymerization which may clog theemulsification system, addition of the initiator may be just after ornear the end of emulsification. In certain embodiments a small amount ofinhibitor may be added to inhibit polymerization during emulsification.

Photoinitiators present in the aqueous phase may be at least partiallywater soluble and may comprise between about 0.05% and about 10%, and incertain embodiments between about 0.2% and about 10% by weight of theoil phase. Lower amounts of photoinitiator allow light to betterpenetrate the HIPE foam, which can provide for polymerization deeperinto the HIPE foam. However, if polymerization is done in anoxygen-containing environment, there should be enough photoinitiator toinitiate the polymerization and overcome oxygen inhibition.Photoinitiators can respond rapidly and efficiently to a light sourcewith the production of radicals, cations, and other species that arecapable of initiating a polymerization reaction. The photoinitiatorsused in the present invention may absorb UV light at wavelengths of fromabout 200 nanometers (nm) to about 800 nm, in certain embodiments fromabout 200 nm to about 350 nm, and in certain embodiments from about 350nm to about 450 nm. If the photoinitiator is in the aqueous phase,suitable types of water-soluble photoinitiators include benzophenones,benzils, and thioxanthones. Examples of photoinitiators include2,2′-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride; 2,2′-Azobis[2-(2-imidazolin-2-yl)propane]disulfate dehydrate;2,2′-Azobis(1-imino-1-pyrrolidino-2-ethylpropane)dihydrochloride;2,2′-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide];2,2′-Azobis(2-methylpropionamidine)dihydrochloride;2,2′-dicarboxymethoxydibenzalacetone,4,4′-dicarboxymethoxydibenzalacetone,4,4′-dicarboxymethoxydibenzalcyclohexanone,4-dimethylamino-4′-carboxymethoxydibenzalacetone; and4,4′-disulphoxymethoxydibenzalacetone. Other suitable photoinitiatorsthat can be used in the present invention are listed in U.S. Pat. No.4,824,765 (Sperry et al.) issued Apr. 25, 1989.

In addition to the previously described components other components maybe included in either the aqueous or oil phase of a HIPE. Examplesinclude antioxidants, for example hindered phenolics, hindered aminelight stabilizers; plasticizers, for example dioctyl phthalate, dinonylsebacate; flame retardants, for example halogenated hydrocarbons,phosphates, borates, inorganic salts such as antimony trioxide orammonium phosphate or magnesium hydroxide; dyes and pigments;fluorescers; filler particles, for example starch, titanium dioxide,carbon black, or calcium carbonate; fibers; chain transfer agents; odorabsorbers, for example activated carbon particulates; dissolvedpolymers; dissolved oligomers; and the like.

HIPE foam is produced from the polymerization of the monomers comprisingthe continuous oil phase of a HIPE. In certain embodiments, HIPE foamsmay have one or more layers, and may be either homogeneous orheterogeneous polymeric open-celled foams. Homogeneity and heterogeneityrelate to distinct layers within the same HIPE foam, which are similarin the case of homogeneous HIPE foams or which differ in the case ofheterogeneous HIPE foams. A heterogeneous HIPE foam may contain at leasttwo distinct layers that differ with regard to their chemicalcomposition, physical properties, or both; for example layers may differwith regard to one or more of foam density, polymer composition,specific surface area, or pore size (also referred to as cell size). Forexample, for a HIPE foam if the difference relates to pore size, theaverage pore size in each layer may differ by at least about 20%, incertain embodiments by at least about 35%, and in still otherembodiments by at least about 50%. In another example, if thedifferences in the layers of a HIPE foam relate to density, thedensities of the layers may differ by at least about 20%, in certainembodiments by at least about 35%, and in still other embodiments by atleast about 50%. For instance, if one layer of a HIPE foam has a densityof 0.020 g/cc, another layer may have a density of at least about 0.024g/cc or less than about 0.016 g/cc, in certain embodiments at leastabout 0.027 g/cc or less than about 0.013 g/cc, and in still otherembodiments at least about 0.030 g/cc or less than about 0.010 g/cc. Ifthe differences between the layers are related to the chemicalcomposition of the HIPE or HIPE foam, the differences may reflect arelative amount difference in at least one monomer component, forexample by at least about 20%, in certain embodiments by at least about35%, and in still further embodiments by at least about 50%. Forinstance, if one layer of a HIPE or HIPE foam is composed of about 10%styrene in its formulation, another layer of the HIPE or HIPE foamshould be composed of at least about 12%, and in certain embodiments ofat least about 15%.

A HIPE foam having separate layers formed from differing HIPEs, asexplained in more detail below, provides a HIPE foam with a range ofdesired performance characteristics. For example, a HIPE foam comprisinga first and second foam layer, wherein the first foam layer has arelatively larger pore or cell size, than the second layer, when used inan absorbent article may more quickly absorb incoming fluids than thesecond layer. By way of example when used in an absorbent articled thefirst foam layer may be layered over the second foam layer havingrelatively smaller pore sizes, as compared to the first foam layer,which exert more capillary pressure and drain the acquired fluid fromthe first foam layer, restoring the first foam layer's ability toacquire more fluid. HIPE foam pore sizes may range from 1 to 200 μm andin certain embodiments may be less than 100 μm. HIPE foams of thepresent invention having two major parallel surfaces may be from 0.05 to10 mm thick, and in certain embodiments 2 mm to 8 mm. The desiredthickness of a HIPE will depend on the materials used to form the HIPE,the speed at which a HIPE is deposited on a belt, and the intended useof the resulting HIPE foam

The HIPE foams of the present invention are relatively open-celled. Thisrefers to the individual cells or pores of the HIPE foam being insubstantially unobstructed communication with adjoining cells. The cellsin such substantially open-celled HIPE foam structures haveintercellular openings or windows that are large enough to permit readyfluid transfer from one cell to another within the HIPE foam structure.For purpose of the present invention, a HIPE foam is considered“open-celled” if at least about 80% of the cells in the HIPE foam thatare at least 1 μm in size are in fluid communication with at least oneadjoining cell.

In addition to being open-celled, in certain embodiments HIPE foams aresufficiently hydrophilic to permit the HIPE foam to absorb aqueousfluids, for example the internal surfaces of a HIPE foam may be renderedhydrophilic by residual hydrophilizing surfactants or salts left in theHIPE foam following polymerization, by selected post-polymerization HIPEfoam treatment procedures (as described hereafter), or combinations ofboth.

In certain embodiments, for example when used in certain absorbentarticles, a HIPE foam may be flexible and exhibit an appropriate glasstransition temperature (Tg). The Tg represents the midpoint of thetransition between the glassy and rubbery states of the polymer. Ingeneral, HIPE foams that have a higher Tg than the temperature of usecan be very strong but will also be very rigid and potentially prone tofracture. In certain embodiments, regions of the HIPE foams of thecurrent invention which exhibit either a relatively high Tg or excessivebrittleness will be discontinuous. Since these discontinuous regionswill also generally exhibit high strength, they can be prepared at lowerdensities without compromising the overall strength of the HIPE foam.

HIPE foams intended for applications requiring flexibility shouldcontain at least one continuous region having a Tg as low as possible,so long as the overall HIPE foam has acceptable strength at in-usetemperatures. In certain embodiments, the Tg of this region will be lessthan about 30° C. for foams used at about ambient temperatureconditions, in certain other embodiments less than about 20° C. For HIPEfoams used in applications wherein the use temperature is higher orlower than ambient, the Tg of the continuous region may be no more that10° C. greater than the use temperature, in certain embodiments the sameas use temperature, and in further embodiments about 10° C. less thanuse temperature wherein flexibility is desired. Accordingly, monomersare selected as much as possible that provide corresponding polymershaving lower Tg's.

The HIPE foams of the present invention may be used as absorbent corematerials in absorbent articles, such as feminine hygiene articles, forexample pads, pantiliners, and tampons; disposable diapers; incontinencearticles, for example pads, adult diapers; homecare articles, forexample wipes, pads, towels; and beauty care articles, for example pads,wipes, and skin care articles, such as used for pore cleaning.

To produce a HIPE using the above, and shown in FIG. 1, an aqueous phase10 and an oil phase 20 are combined in a ratio between about 8:1 and140:1. In certain embodiments, the aqueous phase to oil phase ratio isbetween about 10:1 and about 75:1, and in certain other embodiments theaqueous phase to oil phase ratio is between about 13:1 and about 65:1.This is termed the “water-to-oil” or W:O ratio and can be used todetermine the density of the resulting HIPE foam. As discussed, the oilphase may contain one or more of monomers, comonomers, photoinitiators,crosslinkers, and emulsifiers, as well as optional components. The waterphase will contain water and in certain embodiments one or morecomponents such as electrolyte, initiator, or optional components.

The HIPE can be formed from the combined aqueous 10 and oil 20 phases bysubjecting these combined phases to shear agitation in a mixing chamberor mixing zone 30. The combined aqueous 10 and oil 20 phases aresubjected to shear agitation produce a stable HIPE having aqueousdroplets of the desired size. The emulsion making process produces aHIPE where the aqueous phase droplets are dispersed to such an extentthat the resulting HIPE foam will have the desired structuralcharacteristics. Emulsification of the aqueous 10 and oil 20 phasecombination in the mixing zone 30 may involve the use of a mixing oragitation device such as an impeller, by passing the combined aqueousand oil phases through a series of static mixers at a rate necessary toimpart the requisite shear, or combinations of both. Once formed, theHIPE can then be withdrawn or pumped from the mixing zone 30. One methodfor forming HIPEs using a continuous process is described in U.S. Pat.No. 5,149,720 (DesMarais et al), issued Sep. 22, 1992 and U.S. Pat. No.5,827,909 (DesMarais) issued on Oct. 27, 1998.

In certain embodiments for a continuous process the HIPE can bewithdrawn or pumped from the mixing zone and transported to a heatingzone 50, such as a curing oven by being deposited on to a belt 40travelling in a substantially horizontal direction. An initiator may bepresent in the aqueous phase, or as shown in FIG. 1 an initiator 60 maybe introduced during the HIPE making process, and in certainembodiments, after the HIPE has been formed but before the HIPE has beendeposited on to the belt 40. The HIPE may be deposited on to the beltthrough one or more depositing devices 70 such as a die, sprayer, orcaster. As shown in FIG. 2, in the present invention two or moredistinct HIPEs can be produced, which after polymerization will form twoor more distinct layers in a HIPE foam, for example a first HIPE and asecond HIPE, wherein each HIPE may have an individual composition(aqueous and oil phases) or individual combinations of properties, forexample pore dimensions, mechanical properties, and the like, thatdiffers from the other HIPEs. The individual HIPEs can be formed fromone or more individual oil phases and one or more individual aqueousphases, and combinations thereof. For example, individual HIPEs can beformed from a single oil phase combined with 2 or more different aqueousphases, or as shown in FIG. 2 a single aqueous phase 11 combined with 2or more individual oil phases 21, 22.

The individual aqueous 11 and oil phases 21, 22 enter separate mixingzones 31 and 32 and then are deposited the same way as individual HIPEs.For example, in a continuous process of the present invention a firstdie 71 can deposit one HIPE layer on to a belt 40 then the same die or asecond die 72, as shown in FIG. 2, could deposit a second HIPE on top ofthe first HIPE. In certain embodiments, the top second HIPE may have alower concentration of photoinitiator as compared to the bottom firstHIPE such that a similar amount of radicals is formed in both HIPElayers. In another embodiment using the previously described continuousmethod a die could deposit HIPEs adjacently on to a belt where theindividual HIPEs may or may not overlap each other, or any other meansof moving one or more HIPEs from a mixing zone to produce a HIPE foam.

Examples of belts may include endless belts made of one or more metals,a resin, or combinations thereof or sheet materials such as films thatmay be positioned on the belt and moving therewith. The averagethickness of the HIPE, as measured from the surface of the HIPE that isin contact with the belt to the opposing HIPE surface, can be adjustedby the movement speed of the belt, the flow of HIPE deposited on thebelt, or the configuration of one or more depositing devices used todeposit the HIPE on a belt.

The belt can be any thickness or shape suitable for producing a HIPEfoam. Further, the surface of the belt upon which the HIPE will bedeposited, can be substantially smooth or may comprise depressions,protuberances, or combinations thereof. The protuberances or depressionsmay be arranged in any formation or order and can be used to providepatterns, designs, markings or the like to HIPE foam. The belt maycomprise one or more materials suitable for the polymerizationconditions (various properties such as heat resistance, weatherability,surface energy, abrasion resistance, recycling property, tensilestrength and other mechanical strengths) and may comprise at least onematerial from the group including films, non-woven materials, wovenmaterials, and combinations thereof. Examples of films include, fluorineresins such as polytetrafluoroethylene,tetrafluoroethylene-perfluoroalkylvinyl ether copolymers,tetrafluoroethylene-hexafluoropropylene copolymers, andtetrafluoroethylene-ethylene copolymers; silicone resins such asdimethyl polysiloxane and dimethylsiloxane-diphenyl siloxane copolymers;heat-resistant resins such as polyimides, polyphenylene sulfides,polysulfones, polyether sulfones, polyether imides, polyether etherketones, and para type aramid resins; thermoplastic polyester resinssuch as polyethylene terephthalates, polybutylene terephthalates,polyethylene naphthalates, polybutylene naphthalates, andpolycyclohexane terephthalates, thermoplastic polyester type elastomerresins such as block copolymers (polyether type) formed of PBT andpolytetramethylene oxide glycol and block copolymers (polyester type)formed of PBT and polycaprolactone may be used. These materials may beused either singly or in mixed form of two or more materials. Further,the belt may be a laminate comprising two or more different materials ortwo or more materials of the same composition, but which differ in oneor more physical characteristics, such as quality or thickness. Incertain embodiments the belt or a film positioned on the belt and movingtherewith may be transparent to UV light; allowing the UV light from aUV light source positioned below the belt, film or both to polymerizethe monomers in a HIPE foam.

In certain embodiments, the belt 40 moves the HIPE into a heating zone50 where the monomers present in the HIPE are polymerized. Without beingbound by theory, it is believed that HIPE foam formation comprises twooverlapping processes. These are the polymerization of the monomers andthe formation of crosslinks between active sites on adjacent polymerbackbones.

As used herein the term “polymerize” as in to polymerize monomers toform a HIPE foam, encompass both polymerization of monomers andformation of crosslinks between active sites on adjacent polymerbackbones. Crosslinking provides HIPE foams with strength and integritythat is helpful to their further handling and use. The current inventioninvolves increasing the overall level of polymerization andcross-linking, thereby reducing the amount of unpolymerized monomer inthe HIPE foam. Polymerization can be initiated prior to reaching theheating zone by, for example, preparing the HIPE at a temperaturesufficient to begin polymerization. However, the HIPE is polymerizedbeyond the point of shapability or moldability in the heating zone. Heatfor the heating zone can be, for example, derived from an oven locatedabove and below the HIPE or surrounding the HIPE. Heat can be fromforced air ovens, IR heat lamps, microwave, steam or other suitablesource. As an example of using steam the heat zone may be a steam tunnelwherein the HIPE is exposed to steam, thereby achieving highly efficientthermal transfer as water condenses onto the HIPE.

In certain embodiments, the temperature may be elevated in a step-wisemanner so as to increase the rate of polymerization, initiate drying, orboth as the HIPE becomes more completely polymerized. In addition, thecuring of the HIPE may be accomplished by passing the web through a hotliquid bath composed of any hot liquid of sufficient temperature toinitiate the curing of the monomers. Polymerization temperatures willvary depending on the type of emulsion being cured, the initiator beingused, heat source used, and whether or not the heating zone is sealed,but will typically be above 25° C., often above 50° C. In certainembodiments, polymerization temperatures within the heating zone mayreach between about 50° C. and 150° C. The HIPE is maintained in theheating zone for a time sufficient to polymerize at least 75%,preferably at least 90% of the monomers in the oil phase of the HIPE.Sufficient polymerization of the HIPE may be controlled by a combinationof the initiator used, the temperature of the heat zone, the efficiencyof the heat transfer in the heat zone, the rate at which the HIPE goesthrough the heat zone and the length of the heat zone.

Following the heat zone 50 the belt 40 moves the mostly polymerized HIPEfoam to an Ultraviolet (UV) light zone 80 containing one or more sourcesof UV light. Exposure of the HIPE foam containing unpolymerizedmonomers, and in certain embodiments, one or more photoinitiators to theUV light zone 80 initiates polymerization of unpolymerized monomers inthe oil phase of the HIPE foam following heat assisted polymerization.An examples of a source of UV light is a UV lamp. There may be one ormore sources of UV light used to polymerize the HIPE monomers. A UVlight source may be positioned above or below the belt. The sources maybe the same or differ. For example, the sources may differ in thewavelength of the UV light they produce or in the amount of time a HIPEis exposed to the UV light source. The UV light wavelength in the rangefrom about 200 to about 800 nm, and in certain embodiments from about250 nm to 450 nm, overlaps to at least some degree with the UV lightabsorption band of the photoinitiator and is of sufficient intensity andexposure duration to substantially complete the polymerization of theunpolymerized monomers. Without being limited to theory it is believedthat due to the tendency of emulsions, such as HIPEs, to scatter light,in certain embodiments, long wavelengths in this range should be usedbecause they are better able to penetrate the emulsions. Following theapplication of UV light the HIPE foam contains less than 400 ppm, incertain embodiments less than 100 ppm, and in certain other embodimentsless than detection limits ppm residual or unpolymerized monomer, inless than about 10 minutes, less than about 30 seconds, less than about10 seconds, or less than about 1 second. In certain embodiments, theentire emulsion making, polymerization, and monomer reduction processeswill take less than 20 min, in certain other embodiments in furtherembodiments less than 15 minutes, and in still further embodiments lessthan 5 minutes.

Following polymerization, the resulting HIPE foam is saturated withaqueous phase that needs to be removed to obtain substantially dry HIPEfoam. In certain embodiments, HIPE foams can be squeezed free of most ofthe aqueous phase by using compression, for example by running the HIPEfoam through one or more pairs of nip rollers 90. The nip rollers 90 canbe positioned such that they squeeze the aqueous phase out of the HIPEfoam. The nip rollers 90 can be porous and have a vacuum applied fromthe inside such that they assist in drawing aqueous phase out of theHIPE foam. In certain embodiments, nip rollers 90 can be positioned inpairs, such that a first nip roller 90 is located above a liquidpermeable belt 40, such as a belt 40 having pores or composed of amesh-like material, and a second opposing nip roller 91 facing the firstnip roller 90 and located below the liquid permeable belt 40. One of thepair, for example the first nip roller 90 can be pressurized while theother, for example the second nip roller 91, can be evacuated, so as toboth blow and draw the aqueous phase out the of the HIPE foam. The niprollers may also be heated to assist in removing the aqueous phase. Incertain embodiments, nip rollers are only applied to non-rigid HIPEfoams, that is HIPE foams whose walls would not be destroyed bycompressing the HIPE foam. In yet a further embodiment, the surface ofthe nip rollers may contain irregularities in the form of protuberances,depressions, or both such that a HIPE foam can be embossed as it ismoving through the nip rollers. When the HIPE has the desired dryness itmay be cut or sliced into a form suitable for the intended application.

In certain embodiments, in place of or in combination with nip rollers,the aqueous phase may be removed by sending the HIPE foam through adrying zone 100 where it is heated, exposed to a vacuum, or acombination of heat and vacuum exposure. Heat can be applied, forexample, by running the foam though a forced air oven, IR oven,microwave oven or radiowave oven. The extent to which a HIPE foam isdried depends on the application. In certain embodiments, greater than50% of the aqueous phase is removed. In certain other embodimentsgreater than 90%, and in still other embodiments greater than 95% of theaqueous phase is removed during the drying process.

EXAMPLES

Preparation of High Internal Phase Emulsions (HIPE) and their subsequentpolymerization into absorbent foams are illustrated in the followingexample. The HIPE samples comprised two layers—a bottom layer and a toplayer, wherein the bottom layer had a smaller average pore size of 30microns and the top layer had a larger average pore size of about 80microns.

A. Small Cell Layer Hire Formation

Small Cell Layer Components:

To prepare the bottom small cell layer of the HIPE the aqueous phase,oil phase, and initiator contained the following components as shownbelow in Table 1.

TABLE 1 % Amount Based Oil Phase on Total Weight of Oil Phase2-ethylhexyl acrylate (EHA) 36.7% 2-ethylhexyl methacrylate (EHMA)37.61%  ethyleneglycol dimethacrylate (EGDMA) 17.43%  Dimethyl ammoniummethyl sulfate 0.93% (DTDMAMS) Polyglycerol succinate (PGS) 6.48%Photoinitiator - Darocur 1173* 0.99% % Amount Based on Total AqueousPhase Weight of Aqueous Phase CaCl₂ 3.85% Water:oil ratio 26:1 % AmountBased on Total Initiator in Aqueous Solution Weight of Aqueous SolutionPotassium Persulfate 3.50% Water:oil ratio 1:1 *BASF Corporation,Florham Park, NJ

Equipment:

The smaller celled HIPE is prepared in equipment comprising staticmixers and a recirculation pump. The static mixers are manufactured bySulzer (Sulzer Ltd. Zürcherstrasse 14, 8401 Winterthur, Switzerland).Forty-eight elements of SMX style mixers, sized to fit within a standard1.5″ diameter pipe were used as the primary mixing loop elements. Foursets of twelve elements welded so that each sequential segment isrotated 90° are fitted into independent sections of pipe fitted with 2″tri-clover quick disconnect piping flanges.

The aqueous phase is introduced into a recirculation loop via a modified1⅞″ tubing 90° elbow with 2″ tri-clover quick disconnect piping flanges,with a ½″ pipe welded into the elbow to form an annulus such that theaqueous phase is entering the discharge end of the elbow, concurrentwith the recirculation flow, both proceeding vertically downward. Theend of the annular ½″ pipe is internally threaded and a set screw with a17/64″ hole drilled in it to direct the aqueous incoming flow toward thestatic mixers.

Three sections of the SMX containing pipes, vertically oriented, followthe aqueous introduction elbow. Then the flow is directed by two elbows,both 1⅞″ tubing elbows with tri-clover fittings, first a 90° and then a45°. The final section of SMX mixers is connected upward at a convenientangle to have its discharge at about the same elevation as the inletfittings to the recirculation pump.

The discharge from the final SMX mixer segment goes through a conicalreducer to a ⅞″ Tee. (Tee A). One side of the Tee is connected to a samediameter elbow fitted with a temperature probe, which then connects toanother ⅞″ Tee (Tee B). One side of Tee B connects to a Teflon linedhose 1¼″ in diameter and 48″ long. The hose connects to the stem side ofa ⅞″ Tee (Tee C). One side of Tee C's cross piece is connected upwardlyto the inlet of the recirculation pump, a Waukesha Model 030 U2 lobepump (Waukesha Cherry-Burrell Company, Delavan, Wis.). The other side ofTee C's cross piece in connected downwardly to a ⅞″ to ⅝″ conicalreducer. The small end of the conical reducer uses a ¾″ tri-cloverconnection to a custom made section of ⅜″ stainless steel tubing with a¾″ tri-clover fitting welded onto the tube by first drilling a matchingdiameter hole in a ¾″ tri-clover end cap. This allows the tube toproject into and past the intersection of the stem side of Tee C to thecross piece of Tee C. The end of the tube projecting inward toward theWaukesha pump is internally threaded and fitted with a set screw intowhich a 7/64″ hole has been drilled. The other end of the tube is fittedwith a ¾″ tri-clover fitting facing downward fabricated in the same wayas mentioned above.

The discharge from the Waukesha pump transfers to a 1⅜″ diameter by 6″spool piece with a small port for a temperature probe and tri-cloversanitary fittings, followed by six elements of 1¼″ Kenics helical staticmixers (Chemineer Inc., Dayton, Ohio) in a section of pipe just longenough to contain them, with ends fitted with tri-clover fittings. Nextis a 1⅜″ 90° tubing elbow with tri-clover fittings, a 1⅜″ diameter by 6″spool piece, a second 1⅜″ diameter by 6″ spool piece fitted with a meansto vent gasses from this, the high spot of the total first stage mixingassembly, and then a 1⅜ to 1⅞″ conical spool piece connected to theaqueous injector elbow mentioned above. This completes the descriptionof the mixing stage for the small celled HIPE.

It has been found that the supply pumps or the recirculation pump canlead to cyclic pulsations of flow. To mitigate that behavior, the freeend of Tee A in the above description can be connected to a surgedampener assembly containing a pressure transducer to monitor pressuresand a chamber which can be vented to allow for different volumes of airto be maintained in the chamber in order to dampen the pressurefluctuations.

The discharge from the mixing stage issues from Tee B through a Teflonlined 1¼″ braided steel hose to a 1″ piping elbow fitted with a similarinjector tube arrangement to the aqueous injector elbow described above,but with ⅜″ tubing instead of ½″, and fitted with a set screw with a3/32″ drilled hole. The initiator solution is introduced through thisarrangement. The discharge of the HIPE and the centrally introduced,collinear initiator stream flow are directed to a series of threesegments of twelve elements of SMX mixers sized to fit in a 1″ pipesection with tri-clover fittings. The flow then proceeds through aconical reducer into a custom coat hanger style die. The die thendeposits the HIPE unto an endless belt moving at a speed of 10 metersper minute.

HIRE Formation:

To start this equipment, aqueous phase is heated to about 80 C anddelivered to the aqueous injector point described above at a flow rateof about 2 liters/minute to conveniently fill the equipment and to preheat the equipment to a temperature indicated by the temperatureindicating devices with the loop of about 65 C. The Waukesha pump isstarted at a theoretical rate of 2 liters per minute when aqueous phaseis observed to be coming out of the die, which is higher than the pump,so that the pump is not run dry.

When the equipment temperature is reached, the oil phase is thendelivered to the oil phase injector at a rate of 0.5 kilograms/minute.(Aqueous phases are metered in liters per minute and the oil phase isreferred to in kilograms per minute in order to describe the theoreticaldensity of the polymerized HIPE foam. This also means that one canchange the salt concentration or salt type in the aqueous phase andstill make the same density product without re-calculating flow rates inkilograms to accomplish the desired product). The water to oil ratio atthis stage of startup is then 4:1. After a period of about 5 minutesfrom the first introduction of oil phase, low viscosity HIPE can beobserved issuing from the die. At that point the aqueous temperaturesetpoint is adjusted to about 72 C and the flow rate is uniformlyincreased from 2 liters per minute to 8.107 liters per minute over aperiod of 3 minutes. Only the aqueous phase temperature is controlled,since it is >92% of the total mass of HIPE. The recirculation pump,starting simultaneously with the start of the increase in aqueous phaseflow, is uniformly increased in speed to yield a pumping rate of 28liters per minute over a period of 2 minutes. The oil phase flow, alsobeginning at the same time as the increase in aqueous phase flow, isdecreased uniformly to a flow rate of 0.313 kg/minute over a period of 5minutes. Sodium acrylate flow at 0.031 liters/minute is comingled withthe aqueous flow prior to the introduction to the mixing loop and isgenerally started during the aqueous flow rate ramp. At equilibrium, thewater to oil ratio at the discharge from the recirculation loop is 26:1.The HIPE issuing from the die at the end of the flow ramps is very thickand very white. About 2 minutes after the completion of all of the flowramps, the initiator is introduced at a flow rate of 0.313 liters perminute, bringing the total water to oil ratio to 27:1. When deposited onthe belt that transports the HIPE to the curing chamber with the beltrunning at 10 meters per minute the resulting layer of HIPE isapproximately 2.5 mm thick.

B. Large Cell Layer Hire Formation

Large Cell Layer Components:

To prepare the top large cell layer of the HIPE the aqueous phase, oilphase, and initiator contained the following components as shown belowin Table 2.

TABLE 2 % Amount Based on Oil Phase Total Weight of Oil Phase2-ethylhexyl acrylate (EHA) 72.02%  ethyleneglycol dimethacrylate(EGDMA) 21.51%  dimethyl ammonium methyl sulfate 0.70% (DTDMAMS)Polyglycerol monoisostearate (PGMIS) 5.61% Photoinitiator - Darocur1173* 0.99% % Amount Based on Total Aqueous Phase Weight of AqueousPhase CaCl₂ 3.85% Water:oil ratio 22:1 % Amount Based on Total Initiatorin Aqueous Solution Weight of Aqueous Solution Potassium Persulfate3.50% Water:oil ratio 2:1 *BASF Corporation, Florham Park, NJ

Equipment:

The larger celled HIPE is prepared in equipment comprising two sets ofstatic mixers and two recirculation pumps in two loop arrangements. Thestatic mixers are manufactured by Sulzer (Sulzer Ltd Zürcherstrasse 14,8401 Winterthur, Switzerland). Forty-eight elements of SMX style mixers,sized to fit within a standard 2″ diameter pipe are used as the primarymixing loop elements. Four sets of twelve elements welded so that eachsequential segment is rotated 90° are fitted into independent sectionsof pipe fitted with 2.5″ tri-clover quick disconnect piping flanges.

The aqueous phase is introduced into the recirculation loop via amodified 2⅜″ tubing 90° elbow with 3″ tri-clover quick disconnect pipingflanges, with a ½″ pipe welded into the elbow to form an annulus suchthat the aqueous phase is entering the discharge end of the elbow,concurrent with the recirculation flow, both proceeding verticallyupward at an angle of about 10° to the horizontal.

The end of the annular ½″ pipe is internally threaded and a set screwwith a ⅜″ hole drilled in it to direct the aqueous incoming flow towardthe static mixers. A spool piece, 2⅜″ tubing, 6″ long, with 3″tri-clover fittings connects the injector elbow to two sections of theSMX containing pipes, oriented upward at about 10° to the horizontal.Then the flow is turned to the reverse by two elbows, both 90° 2⅜″tubing elbows with tri-clover fittings. The final two sections of SMXmixers are connected to a conical adapter that starts at 2⅜″ and expandsto 2⅞″. The conical adaptor connects to the stem end of a 2⅞″ tubing Tee(Tee A) fitted with a pressure transducer in the middle of theintersection between the stem and cross piece of the Tee. One side ofTee A connects to a 2⅞″ to 1⅜″ conical adapter, and then to a 1⅜″, 90°elbow, then two 1⅜″ 45° elbows. The use of multiple elbows facilitatesthe fitting together of the large number of piping segments. From the45° elbows, the flow continues to a 1⅜″ diameter, 2″ long spool piece,followed by a 1 5/16″ diameter, 26¼″ spool piece into the stem side of a1⅜″ tubing Tee (Tee B). The upper cross opening of Tee B connects to theoil injector assembly, comprising a 1⅜″ to ⅝″ conical spool piececonnected to an injector similar to the one mentioned above for thesmaller celled HIPE oil injector. The lower cross opening of Tee B isattached to a Waukeshaw Model 30 U2 lobe pump. The discharge from theWaukeshaw pump connects to a 1⅜″, 90° elbow and then to six elements ofKenics helical static mixers in a 1¼″ pipe. A 1⅜″, 90° elbow and then a1⅜″, 45° elbow are next, and then another six element section of Kenicshelical static mixers in a 1¼″ pipe. After that, a 1⅜″ spool piece witha temperature probe fitting and a 1⅜″, 90° elbow and finally a 1⅜″ to2⅜″ spool piece connect to the aqueous injector equipped 2⅜″ tubing 90°elbow.

The other cross exit of Tee A connects to a cross piece of the secondaryaqueous injector Tee, Tee C (2⅞″). The aqueous injector tube, ⅝″, entersthe top of the Tee directed to be annular to the stem side of the Tee,and is fitted with a set screw drilled with a 5/16″ hole. The stem sideof Tee C connects to two 2½″ standard pipe sections of twelve elementsof SMX static mixers, and then to two 2⅞″ 90° tubing elbows directingthe flow back toward Tee C, but above it due to the approximately 10°upward slant both the outward bound and inward bound piping section haverelative to horizontal. This arrangement was chosen to minimizeentrained air in the mixers, and avoids the need for venting as is usedin the smaller celled HIPE setup. The last two section of 2½″ SMX mixersdischarge their flow into another 2⅞″ tubing Tee equipped with apressure transducer, again at the intersection of the cross and stempieces of the Tee, Tee D. One side of the Tee D cross piece connects toa 2⅞″ 90° tubing elbow and then into a Waukeshaw Model 130 U2 lobe pump.The lower discharge of the pump connects to a 2⅞″ 90° tubing elbow witha temperature probe fitting and connects to the cross piece end of a 2⅞″tubing Tee, Tee E. The other cross piece end of Tee E connects to across piece end of Tee C, completing the second mixing stage loop.

The stem side of Tee E connects to 2⅞″ to 1⅜″ conical reducer and thento a 1⅜″ 90° tubing elbow, and then to a surge dampener assembly similarto the one described in the aforementioned small celled HIPE setup. Theremaining end of Tee D similarly goes to a 2⅞″ 90° tubing elbow and thento a 2⅞″ to 1⅜″ conical reducer and then to a the cross piece side of a1⅜″ tubing Tee, Tee G. The other cross piece end of Tee G goes toanother surge dampener, while the stem side of Tee G goes to a 1⅜″×33″Teflon lined flex hose.

The flex hose connects to the initiator mixer assembly through a 1⅜″ 90°tubing elbow equipped with a ⅜″ injector tube equipped with a ¼″ setscrew with a ⅛″ hole. The initiator and HIPE are then mixed inforty-eight elements of SMX static mixers sized to fit within a 1.75″diameter pipe. Again, twelve elements are welded together for each offour piping segments. The HIPE then passes through a conical reducer toa coat hanger style die, and the HIPE waterfalls onto the smaller cellsized HIPE passing underneath the die.

HIRE Formation:

To start up the system, aqueous phase is delivered to the first stageinjector at a rate of 2 liters per minute at a temperature of about 80C, and the second injector at a rate of 1 liter per minute at the sametemperature. When aqueous phase is observed coming out of the die, whichis higher than any of the pumps, the pumps are started. When theinternal temperature indicated by the temperature probes all exceed 65C, the oil phase is introduced to the oil injector at a rate of 0.50kg/minute. After several minutes, when HIPE is observed issuing from thedie, the first aqueous temperature target is shifted to 75 C and theflow rate changed to 2.828 liters per minute uniformly over a time of 3minutes. At the same time the oil phase flow rate is lowered to 0.202kg/minute over a period of 5 minutes, the first recirculation pump isincreased uniformly to 8 liters per minute over 3 minutes and the sodiumacrylate solution feed is started at a flow rate of 0.02 liters perminute, mixing with the aqueous phase prior to introduction into themixing loop. After the flow rate changes are completed, the secondaqueous flow is increased from 1 liter/minute to 1.596 liters per minuteover a period of two minutes.

At the completion of the second aqueous flow ramp, the initiatorsolution is introduced to the initiator injector at a flow rate of 0.404liters per minute. The HIPE provided to the 0.33 meter wide die is thenat an internal phase ratio of 24:1, and the layer thickness whenprovided on top of the smaller celled HIPE passing by at 10 meters perminute is 1.5 mm.

The HIPE is then transferred by the belt to a curing oven forpolymerization of the monomers. The internal temperature of the oven ismaintained at about 100° C. The HIPE resides in the curing oven forabout 8 minutes.

Following the curing oven the HIPE is passed under (at a speed of 10meters per minute) a UV lamp (I300MB irradiator using P300MT powersupply; Fusion UV Systems, Inc., Gaithersburg, Maryland) equip with a 4″long 300 W/inch Fusion H+ bulb in conjunction with a LC-6B bench-topconveyor (Fusion UV Systems, Inc.).

Quantitative light measurements for a single pass under the UV lamp areshown in Table 3. The measurements were taken with a Power Puck (10Watt, EIT, Sterling, Va.). To simulate multiple passes under a UV lamp;once the sample has passed under the UV lamp it was removed from thebelt and then placed back on the belt, such that the sample would passunder the UV lamp again. This process was then repeated as necessary.

TABLE 3 First UV Lamp Spectral Range Joules/cm² Watts/cm² UVA 1.46 3.37UVB 0.49 1.11 UVC 0.04 0.09 UVV 0.95 2.08

C. Test Methods

Four HIPE foam samples (including both the top and bottom layer)produced by the method described above were measured to determine theconcentration of residual (unpolymerized) monomers, using a gaschromatograph (GC) with a capillary column and a flame ionizationdetector (FID). Excessive levels of unpolymerized monomers areindicative of problems in the method used to produce HIPE foam. Monomersmeasured in this method include ethylhexyl acrylate (EHA), ethylhexylmethacrylate (EHMA), and ethylene glycol dimethacrylate (EGDMA).

Equipment

-   -   Gas Chromatograph . . . Agilent G2630B-6850 Series with flame        ionization detector (Agilent Technologies, Wilmington, Del), or        equivalent.    -   Autosampler . . . Agilent G2880B-6850 Series (Agilent        Technologies), or equivalent.    -   GC Control Station . . . Agilent G1875BA ChemStation PC Bundle        (Agilent Technologies), or equivalent.    -   Capillary Column . . . J&W Scientific DB-5, 30 m×0.32 mm I.D.        with 0.25 um film (Agilent Technologies—part no. 123-5032), or        equivalent.    -   Injector . . . 1 uL splitless injector.    -   Balance . . . Analytical balance with resolution of 0.1 mg    -   Pipette, variable . . . Capable of delivering 0.25, 0.50, and        1.0 mL aliquots (such as VWR cat. no. 83009-170 variable volume        100-1000 uL pipette).    -   Vial, 40 mL . . . CS200 clear glass vials (VWR cat. no.        80076-562), with Teflon-lined plastic caps (VWR cat. no.        16161-213), or equivalent.    -   Vial, 2 mL . . . Clear glass vials (VWR cat. no. 66030-002),        with septum caps (VWR cat. no. 69400-043), or equivalent.    -   Cyclohexane . . . HPLC grade, 99.9+ % purity (Sigma-Aldrich cat.        no. 270628).    -   EHA Standard . . . (Sigma-Aldrich cat. no. 290815).    -   EHMA Standard . . . (Sigma-Aldrich cat. no. 290807).    -   EGDMA Standard . . . (Sigma-Aldrich cat. no. 335681).    -   Dispenser . . . EMD Optifix Solvent-50 bottle-top dispenser for        cyclohexane (EMD Chemicals, Inc., Gibbstown, N.J.—part no.        10108148-1), or equivalent.    -   Helium Gas . . . GC grade (ultra-high purity).    -   Hydrogen Gas . . . GC grade (ultra-high purity).    -   Nitrogen Gas . . . GC grade (ultra-high purity).    -   Air . . . GC grade (ultra-high purity).    -   Transfer Pipets . . . Disposable plastic pipets, such as Samco        cat. no. 232 (Samco Scientific Corp., San Fernando, Calif.), or        equivalent.

Test Procedure

GC Operating Conditions

-   -   Inlet Temp . . . 280° C.    -   Injection Volume . . . 1 uL    -   Purge Time . . . 30 s    -   Purge Flow . . . 30 mL/min Helium    -   Column Flow . . . 1.5-3.0 mL/min Helium    -   Initial Temp . . . 90° C.    -   Initial Time . . . 17-18 min    -   Detector Temp . . . 300° C.    -   Detector Gas Flows . . . 20 mL/min Nitrogen (makeup); 30 mL/min        Hydrogen; 400 mL/min Air    -   EHA Ret. Time . . . 9.5-11.5 minutes    -   EHMA Ret. Time . . . 11.8-15.3 minutes    -   EGDMA Ret. Time . . . 12.0-15.8 minutes

Calibration

1. Weigh 50 +/−5 mg of EHA Standard (recording the actual weight to thenearest 0.1 mg) into a 50 mL volumetric flask, dilute to volume withcyclohexane, stopper, and mix well.

2. Weigh approximately 50 +/−5 mg of EHMA Standard (recording the actualweight to the nearest 0.1 mg) into a separate 50 mL volumetric flask,and dilute to volume with cyclohexane, stopper, and mix well.

3. Weigh approximately 50 +/−5 mg of EGDMA Standard (recording theactual weight to the nearest 0.1 mg) into a separate 50 mL volumetricflask, and dilute to volume with cyclohexane, stopper, and mix well.

4. Into a single 25 mL volumetric flask, pipette 1.0 mL from each of thethree flasks prepared above, dilute to volume with cyclohexane, stopper,and mix well (resulting in a combined standard containing 40 +/−4 ug/mLof EHA, EHMA, and EGDMA).

5. Pipette 0.25 mL from the solution prepared in Step 4 into a 50 mLvolumetric flask, dilute to volume with cyclohexane, stopper, and mixwell (resulting in a combined 0.2 ug/mL standard).

6. Pipette 0.25 mL from the solution prepared in Step 4 into a 25 mLvolumetric flask, dilute to volume with cyclohexane, stopper, and mixwell (resulting in a combined 0.4 ug/mL standard).

7. Pipette 0.25 mL from the solution prepared in Step 4 into a 10 mLvolumetric flask, dilute to volume with cyclohexane, stopper, and mixwell (resulting in a combined 1.0 ug/mL standard).

8. Pipette 0.50 mL from the solution prepared in Step 4 into a 10 mLvolumetric flask, dilute to volume with cyclohexane, stopper, and mixwell (resulting in a combined 2.0 ug/mL standard).

9. Pipette 1.0 mL from the solution prepared in Step 4 into a 10 mLvolumetric flask, dilute to volume with cyclohexane, stopper, and mixwell (resulting in a combined 4.0 ug/mL standard).

10. Fill six separate 2 mL vials with the following: (1)=cyclohexaneonly (blank); (2)=0.2 ug/mL standard; (3)=0.4 ug/mL standard; (4)=1.0ug/mL standard; (5)=2.0 ug/mL standard; (6)=2.0 ug/mL standard.

11. Tightly cap each vial with a septum cap and load the vials in theautosampler (ensuring to maintain the (1) through (6) order).

12. Initiate the GC analysis program.

13. Based on the actual weights of EHA, EHMA, and EGDMA recorded insteps 1-3 above, combined with the results from analysis of the 6standard vials from step 12, utilize the GC's linear regressioncalibration program to generate standard curves of Peak Area vs.Concentration for each monomer.

Sample Testing

1. Use a razor knife to obtain a HIPE foam specimen strip weighing0.20-0.40 g.

2. Weigh the strip on the analytical balance and record the weight (ingrams) to the nearest 0.1 mg.

3. Use a scissors to cut the strip into small pieces (approximately 1cm×1 cm) and transfer the pieces into a 40 mL vial.

4. Use the bottle-top dispenser to add 30 mL of cyclohexane to the vial.

5. Tightly cap the vial and invert 3 times, ensuring all the specimenpieces are thoroughly wetted, to initiate extraction of residualmonomers into cyclohexane.

6. Store the vial undisturbed for at least 16 hours to allow extractionto continue.

7. Invert the vial 3 more times to complete the extraction phase.

8. Use a fresh (unused) disposable pipet to fill a 2 mL vial withcyclohexane extract from the 40 mL vial into a 2 mL vial.

9. Tightly cap the 2 mL vial and load the vial into the GC sampler.

10. Initiate the GC analysis program.

Reporting

Program the GC so the output is in units of ug/mL. Multiply this outputby 30 mL, then divide the product by the sample weight (g) from step 2above, giving a result in units of ug/g. Report the EHA, EHMA, and EGDMAconcentration to the nearest whole ug/g.

The four HIPE samples prepared and tested as described above were testedfor levels of unpolymerized ethylhexyl acrylate (EHA) monomer, theresults of which are shown in the graph of FIG. 3. The levels ofunpolymerized EHA monomer were measured and averaged between the foursamples and depicted in the graph of FIG. 3. The graph shows followingpolymerization in the curing oven the samples hade an average level ofunpolymerized EHA monomer of about 1400 ppm. Following exposure of theHIPE samples to UV light the amount of unpolymerized EHA monomerdecreased to almost undetectable amounts following continued exposure toUV light; demonstrating that the methods of the present invention reducethe amount of unpolymerized monomer following polymerization of a HIPEto a HIPE foam.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A High Internal Phase Emulsion foam formed by polymerizing a HighInternal Phase Emulsion comprising: a) an oil phase comprising i)monomer; ii) cross-linking agent; iii) emulsifier; b) aqueous phase; c)photoinitiator; wherein the High Internal Phase Emulsion foam comprisesless than 400 ppm unpolymerized monomer.
 2. The High Internal PhaseEmulsion foam of claim 1 comprising less than 100 ppm unpolymerizedmonomer.
 3. The High Internal Phase Emulsion of claim 1, wherein thephotoinitiator is present in an amount between about 0.05% and 10%photoinitiator by weight of the oil phase.
 4. The High Internal PhaseEmulsion of claim 1, wherein the photoinitiator absorbs UV light atwavelengths of about 200 nm to about 800 nm.
 5. The High Internal PhaseEmulsion of claim 1, wherein the photoinitiator is at least one ofbenzyl ketals, α-hydroxyalkyl phenones, α-amino alkyl phenones, oracylphospine oxides.
 6. The High Internal Phase Emulsion of claim 1,wherein the aqueous phase comprises an initiator.
 7. The High InternalPhase Emulsion of claim 6, wherein the initiator is at least one ofammonium persulfate, sodium persulfate, potassium persulfate, or2,2′-azobis(N,N′-dimethyleneisobutyramidine)dihydrochloride.
 8. The HighInternal Phase Emulsion of claim 1, wherein monomer is at least one ofalkyl acrylate or alkyl methacrylate.
 9. The High Internal PhaseEmulsion of claim 3, wherein the monomer is at least one of ethylhexylacrylate, butyl acrylate, hexyl acrylate, octyl acrylate, nonylacrylate, decyl acrylate, isodecyl acrylate, tetradecyl acrylate, benzylacrylate, nonyl phenyl acrylate, hexyl methacrylate, 2-ethylhexylmethacrylate, octyl methacrylate, nonyl methacrylate, decylmethacrylate, isodecyl methacrylate, dodecyl methacrylate, tetradecylmethacrylate, or octadecyl methacrylate.
 10. The High Internal PhaseEmulsion of claim 1, wherein emulsifier is at least one of sorbitanmonoesters of branched C₁₆-C₂₄ fatty acids; linear unsaturated C₁₆-C₂₂fatty acids; inear saturated C₁₂-C₁₄ fatty acids, polyglycerolmonoesters of—branched C₁₆-C₂₄ fatty acids, linear unsaturated C₁₆-C₂₂fatty acids, linear saturated C₁₂-C₁₄ fatty acids, diglycerolmonoaliphatic ethers of—branched C₁₆-C₂₄ alcohols, linear unsaturatedC₁₆-C₂₂ alcohols,or linear saturated C₁₂-C₁₄ alcohols.
 11. A HighInternal Phase Emulsion foam formed by polymerizing a High InternalPhase Emulsion comprising: a) a first layer having 1) an oil phaseincluding i) monomer; ii) cross-linking agent; iii) emulsifier; 2)aqueous phase; 3) photoinitiator; b) a second layer having 1) an oilphase including i) monomer; ii) cross-linking agent; iii) emulsifier; 2)aqueous phase; 3) photoinitiator; wherein the High Internal PhaseEmulsion foam comprises less than 400 ppm unpolymerized monomer.
 12. TheHigh Internal Phase Emulsion foam of claim 11 comprising less than 100ppm unpolymerized monomer.
 13. The High Internal Phase Emulsion of claim11, wherein the first or second layer comprises between about 0.05% and10% photoinitiator by weight of the oil phase.
 14. The High InternalPhase Emulsion of claim 11, wherein the first or second layer comprisesphotoinitiator that absorbs UV light at wavelengths of about 200 nm toabout 800 nm.
 15. The High Internal Phase Emulsion of claim 11, whereinthe first or second layer comprises photoinitiator that is at least oneof benzyl ketals, α-hydroxyalkyl phenones, α-amino alkyl phenones, oracylphospine oxides.
 16. The High Internal Phase Emulsion of claim 11,wherein the aqueous phase of the first or second layer comprises aninitiator.
 17. The High Internal Phase Emulsion of claim 16, wherein theinitiator is at least one of ammonium persulfate, sodium persulfate,potassium persulfate, or2,2′-azobis(N,N′-dimethyleneisobutyramidine)dihydrochloride.
 18. TheHigh Internal Phase Emulsion of claim 11, wherein the monomer from thefirst or second layer is at least one of alkyl acrylate or alkylmethacrylate.
 19. The High Internal Phase Emulsion of claim 18, whereinthe monomer is at least one of ethylhexyl acrylate, butyl acrylate,hexyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, isodecylacrylate, tetradecyl acrylate, benzyl acrylate, nonyl phenyl acrylate,hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, nonylmethacrylate, decyl methacrylate, isodecyl methacrylate, dodecylmethacrylate, tetradecyl methacrylate, or octadecyl methacrylate. 20.The High Internal Phase Emulsion of claim 11, wherein emulsifier fromthe first or second layer is at least one of sorbitan monoesters ofbranched C₁₆-C₂₄ fatty acids; linear unsaturated C₁₆-C₂₂ fatty acids;inear saturated C₁₂-C₁₄ fatty acids, polyglycerol monoesters of—branchedC₁₆-C₂₄ fatty acids, linear unsaturated C₁₆-C₂₂ fatty acids, linearsaturated C₁₂-C₁₄ fatty acids, diglycerol monoaliphatic ethersof—branched C₁₆-C₂₄ alcohols, linear unsaturated C₁₆-C₂₂ alcohols,orlinear saturated C₁₂-C₁₄ alcohols.